Generally, electromagnetic waves which propagate in space can be long waves, medium frequency waves, microwaves, millimeter waves, infrared light, ultraviolet rays, X-rays, and gamma rays. The electromagnetic waves of each band are used in many fields. Regarding electromagnetic waves in these bands, the electromagnetic waves of the light wave band of the range of 380-760 mm wavelength are visible light to human eyes. Electromagnetic waves from the millimeter wave band to the light wave band are now beginning to be used in the field of communications.
Conventionally, metal reflecting plates are used for the reflecting plate of the millimeter wave band used by the telecommunications sector. However, when using this reflecting plate with a light wave band, in order to form rectangular-type shapes like a cube corner, high angle accuracy is required. Similarly, in order to form the surface smoothly, high surface smoothness is required. A dielectric lens which has omnidirectionality is used where the wavelength of electromagnetic waves is longer than the millimeter wave band. One such dielectric lens is a Luneberg lens formed by adjusting a dielectric constant with styrene foam, etc.
As an example of a device which uses a spherical dielectric lens, the Luneberg lens is used as an antenna. As shown in FIG. 25, in antenna device 111, foam material layer 134 is formed by filling up a foam material between spherical lens 114 and radome 133. This foam material layer 134 has combined spherical lens 114 and radome 133. Thus, spherical lens 114 has structure held at radome 133. Such a device is illustrated in patent document JP 2001-102857 A.